Stability of alpha-amylase immobilized on poly(methyl methacrylate-acrylic acid) microspheres

Poly(methyl methacrylate-acrylic acid) microspheres were prepared and the acid groups were activated by using either carbodiimide (CDI) or thionyl chloride (SOCl2). alpha-Amylase was covalently bound on these activated microspheres. The properties of the immobilized enzyme vv ere investigated and compared with those of the free enzyme. The relative activities were found to be 80.4 and 67.5% for carbodiimide and thionyl chloride bound enzymes, respectively. Maximum activities were obtained at lower pHs and higher temperatures upon immobilization compared to free enzyme. No change in V-max and approximately 12-fold increase in K-m,were observed for immobilized enzymes. The enzyme activities, after storage for 1 month, were found to be 24.5 and 52.5% of I:he initial activity values for CDI and SOCl2, activated matrices, respectively. On the other-hand the free enzyme lost its activity completely in 20 days. Immobilization, storage stability and repeated use capability experiments carried out in the presence of Ca2+ ions demonstrated higher stability, such as SOCl2,immobilized enzyme retained 83.7% and CDI immobilized enzyme retained 90.3% of the original activity of the enzyme. Thf immobilized enzymes that were used 20 times in 3 days in repeated batch experiments demonstrated that, in the absence of Ca2+ ions about 75% and in the presence of Ca2+ ions greater than 90% of the original enzyme activity was retained

Covalent immobilization of alpha-amylase onto poly(2-hydroxyethyl methacrylate) and poly(styrene-2-hydroxyethyl methacrylate) microspheres and the effect of Ca2+ ions on the enzyme activity

alpha-Amylase (1,4-alpha-D-glucan-glucanohydrolase; EC 3.2.1.1, Type VI-B from porcine pancreas, extra pure 29 units mg(-1)) was covalently immobilized on poly (2-hydroxyethyl methacrylate), p(HEMA), and poly (styrene-2-hydroxyethyl methacrylate), p(St-HEMA) microspheres, which were activated by using epichlorohydrin (ECH). The properties of the immobilized enzyme were investigated and compared with those of the free enzyme. For the assays carried out at 25 degrees C and pH 6.9, the relative activities were found to be 61.7 and 67.0% for ECH-activated P(HEMA) and P(St-HEMA) bound enzymes, respectively. The maximum activities were obtained at lower pH values and higher temperatures upon immobilization compared to free enzyme. Kinetic parameters were calculated as 2.51, 22.4 and 6.62 g dm(-3) for K-m and 1.67 x 10(-3), 1.63 x 10(-3) and 1.35 x 10(-3) g dm(-3) min(-1) for V-max in the case of free, P(HEMA) and P(St-HEMA) bound enzymes, respectively. Enzyme activity was found to be ca. 38.9% for ECH-activated P(HEMA) bound enzyme after storage for 1 month. On the other hand, free enzyme lost its activity completely in 20 days. Immobilization, storage stability and repeated use capability experiments that were carried out in the presence of Ca2+ ions demonstrated higher stability. The enzymes immobilized in the presence of Ca2+ ions retained 90.7 and 80.0% of their original activities even after 30 days for ECH-activated P(HEMA) and P(St-HEMA) systems, respectively. In repeated batch experiments, 20 uses in 3 days, in the absence of Ca2+ ions, retention of 79% of the original enzyme activities was observed for ECH-activated P(HEMA) immobilized enzymes. On addition of Ca2+ ions to the assay medium, 90.0 and 80.0% of retention was observed for ECH-activated P(HEMA) and P(St-HEMA) systems, respectively. (C) 1999 Published by Elsevier Science Ltd. All rights reserved

Covalent immobilization of alpha-amylase onto poly(methyl methacrylate-2-hydroxyethyl methacrylate) microspheres and the effect of Ca2+ ions on the enzyme activity

alpha-Amylase was covalently immobilized onto poly(methyl methacry late-2-hydroxyethyl methacrylate) microspheres, which were activated by using either epichlorohydrin (ECH) or cyanuric chloride (C3N3Cl3). The properties of the immobilized enzyme were investigated and compared with those of the free enzyme. For the assays carried out at 25 degrees C and pH 6.9, the relative activities were found to be 73.0 % and 90.8 % for epichlorohydrin and cyanuric chloride bound enzymes, respectively. Upon immobilization, the maximum activities were obtained at lower pH values and higher temperatures as compared with the free enzyme. Kinetic parameters were calculated as 2.51 g/L, 28.54 g/L and 15.50 g/L for K-m and 1.67 x 10(-3) gL(-1) min(-1), 2.89 x 10(-4)gL(-1) min(-1) and 1.89 x 10(-3) gL(-1) min(-1) for V-max for free, epichlorohydrin and cyanuric chloride bound enzymes, respectively. Enzyme activities were found be ca. 32.7 % for ECH and 41.1 % for C3N3Cl3 activated matrices after storage for one month. On the other hand the free enzyme lost its activity completely within 20 days. Immobilization, storage stability and repeated use capability experiments carried out in the presence of Ca2+ ions demonstrated higher stability in the presence of these ions. The enzymes immobilized in the presence of Ca2+ ions retained 90.6 % and 90.8 % of the original activities even after 30 days in the case of ECH and C3N3Cl3 activations, respectively

Covalent immobilization of invertase on chemically activated poly(2-hydroxyethyl methacrylate) microbeads

HASIRCI, Nesrin/0000-0002-4497-0194WOS: 000245091400024Properties of invertase immobilized on poly(2-hydroxyethyl methacrylate) microbeads activated by epichlorohydrin or cyanuric chloride were studied. After 20 repeated uses for 3 days, the activity of the immobilized enzyme was 92-93%

Hemilaminectomy and Bilateral Decompression for Thoracic Spinal Stenosis.

AIM: To assess the effectiveness and reliability of hemilaminectomy and bilateral decompression (HLBD) for the treatment of thoracic spinal stenosis (TSS) in selected patients

Semi-interpenetrating polymer networks (IPNs) for entrapment of glucose isomerase

Glucose isomerase (GI) was entrapped in three different hydrogels such as poly(acrylamide), semi-interpenctrating poly(acrylamide)/K-carrageenan, and poly(acrylamide)/alginate polymer networks. The values for pH optimum and temperature for free and immobilized glucose isomerase were found to be the same as 7.5 and 60 degrees C, respectively. The K-m values for free and immobilized enzyme in poly(acrylamide), poly(acrylamide)/K-carrageenan and poly(acrylamide)/alginate matrices were determined as 18.87, 1.22, 2.78, and 4.54 mg/mL, respectively, while the V-max values for the same systems calculated as 2.51, 0.63, 0.72, and 0.82 mg/mL min, respectively. The storage stability values of immobilized enzyme systems were observed as 81%. 33% and 32%, respectively, after 42 days. In addition to this, it was observed that, after 25th use in 5 days, the retained activities for immobilized enzyme in poly(acrylamide), and semi-interpenetrating polymer networks of poly(acrylamide)/K-carrageenan and poly(acrylamide)/alginate matrices were found as 98%, 71% and 72%, respectively

Rapid emergence of colistin resistance and its impact on fatality among healthcare-associated infections.

This article describes the emergence of resistance and predictors of fatality for 1556 cases of healthcare-associated Gram-negative bloodstream infection in 2014 and 2015. The colistin resistance rate in Klebsiella pneumoniae was 16.1%, compared with 6% in 2013. In total, 660 (42.4%) cases were fatal. The highest fatality rate was among patients with Acinetobacter baumannii bacteraemia (58%), followed by Pseudomonas aeruginosa (45%), Klebsiella pneumoniae (41%), Enterobacter cloacae (32%) and Escherichia coli (28%). On multi-variate analysis, the minimum inhibitory concentrations for carbapenems [odds ratio (OR) 1.02, 95% confidence interval (CI) 1.01-1.04; P = 0.002] and colistin (OR 1.1, 95% CI 1.03-1.17; P = 0.001) were found to be significantly associated with fatality. (C) 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved